Security is an important requirement in many document printing applications. In situations such as official or government document printing, event ticket printing, financial instrument printing and the like, many printed documents must be protected against copying, forging and/or counterfeiting.
One example of such a document is a prescription for medication. Upon receipt of a printed prescription, the pharmacist would like to have a good level of confidence that the document is genuine and is being used only once, by the person to which the prescription was issued. In applications such as this it is important that the document have a security feature that is difficult or impossible to copy, so that a single, valid, original prescription document is not used to create counterfeit copies that also contain the security feature. A security mark that does not survive reproduction is commonly called “fragile.”
Another example document is a confidential company customer list. In this situation, the document's creator may be concerned about the document falling into unauthorized hands and being altered. Thus, in a situation such as this, it is important that the security mark survive reproduction and distribution so that the document can tracked and/or the security mark decoded. A mark that does survive reproduction is commonly called “robust.”
A correlation mark is an example of a security mark that is typically robust. A correlation mark includes one or more elements that are invisible or hardly visible on a printed document. The hidden elements become visible when the document is viewed through a correlation mask that serves as a “key” to the correlation mark.
Security markings that are fragile often require special printing materials, which can increase their costs. Accordingly, the inventors have found to be desirable to provide a security mark that includes elements of a correlation mark, but which also contains fragile components.
This document describes methods and systems for creating and using a security mark that addresses at least some of the problems described above, and/or other problems.